Que tal el:
GeCube GC-R9550L-C3H (Retail) €59
MSI RX9550SE-TD (Retail) €44
MSI RX9550SE-TD128 (Retail) €57
MSI RX9600LE-T (Retail) €72

Todos son DirectX 9. No notaras diferencia entre 64- y 128-bits en un HTPC.